Walking burns more calories

Walking is the most common exercise, and many walkers like to count how many calories are burned. Little known, however, is that the leading standardised equations used to predict or estimate walking energy expenditure — the number of calories burned — assume that one size fits all. They’ve been in place for close to half a century and were based on data from a limited number of people.

A new study at Southern Methodist University, Dallas, found that under firm, level ground conditions, the leading standards are relatively inaccurate and have significant bias. The standards predicted too few calories burned in 97 per cent of the cases researchers examined, said SMU physiologist Lindsay Ludlow.

A new standardised equation developed by SMU scientists is about four times more accurate for adults and kids together, and about two to three times more accurate for adults only, Ludlow said.

“Our new equation is formulated to apply regardless of the height, weight and speed of the walker,” said Ludlow, a researcher in the SMU Locomotor Laboratory of biomechanics expert Peter Weyand. “And it’s appreciably more accurate.”

Ludlow and her colleagues report the new equation in the Journal of Applied Physiology, “Energy expenditure during level human walking: seeking a simple and accurate predictive solution. The economy of level walking is a lot like shipping packages — there is an economy of scale,” said Weyand, a co-author on the paper. “Big people get better gas mileage when fuel economy is expressed on a per-pound basis.”

The SMU equation predicts the calories burned as a person walks on a firm, level surface. Ongoing research is expanding the algorithm to predict the calories burned while walking up and downhill, and while carrying loads, Ludlow said.

The new equation achieves greater accuracy by better incorporating the influence of body size, and by specifically incorporating the influence of height on gait mechanics. Specifically:

Bigger people burn fewer calories on a per pound basis of their body weight to walk at a given speed or to cover a fixed distance

The older standardised equations don’t account for size differences well, assuming roughly that one size fits all.